1. Field of the Invention
The invention relates in general to a method for processing a component error, and more particularly to a method for calibrating multiple audio receivings for noise suppression.
2. Description of the Related Art
Mobile applications have become more and more common with constant lightweight and miniaturization development trends of electronic devices. Small-size electronic devices, such as cell phones and tablet computers, can be applied for voice communication in various occasions. These occasions may be extremely quite or may contain diversified background noises. If the electronic device applied has only one single audio receiving module, such background noises may be recorded during the voice communication to possibly cover a sound from a speaker. The speaker may then need to raise the voice volume in order to allow a recipient to hear the speaker clearly. However, in certain public occasions, raising the voice volume may be an impolite gesture, and private contents of the voice communication may also be inappropriate to be heard by others nearby.
In view of the above reasons, more up-to-date electronic devices are usually equipped with multiple audio receiving modules. With a position difference between two audio receiving modules, background noises can be filtered out such that a speaker need not raise the voice volume. FIG. 1 shows a schematic diagram of a conventional electronic device 100, which may be a common cell phone.
In FIG. 1, a head of a user (speaker) is depicted, and the electronic device 100 is closely located near one side of the face of the user. The electronic device 100 includes a first audio receiving module 110 at one end and an audio speaker module 120 at the other end. The electronic device 100 further includes a second audio receiving module 112 at a position farther away from the first audio receiving module 110. In general, the first audio receiving module 110 and the audio speaker module 120 are located at one side of the face, and the second audio receiving module 112 is located at an opposite side of the electronic device 100. In practice, the second audio receiving module 112 may be located at another position of the electronic device 100, e.g., right at top of the electronic device 100.
The mouth of the user is an audio source 102. When the user makes a sound, sound waves sequentially reach the first audio receiving module 110 and the second audio receiving module 112. Background noises that are simultaneously formed may be regarded as simultaneously arriving the first audio receiving module 110 and the second audio receiving module 112. The first audio receiving module 110 is closer to the audio source 102 than the second audio receiving module 112, and the second audio receiving module 112 is located at an outer side of the user face instead of at an inner side of the user face as the first audio receiving module 110. Thus, a processing module (not shown) in the electronic device 100 can compare audio signals received by the two audio receiving modules 110 and 112 using signal processing. As the background noises reduced by the two audio receiving modules 110 and 112 are substantially the same, the difference between the two is the sound from the audio source 102. Further, when the user does not make a sound while the remote-end audio speaker module 120 sends a sound, the processing module (not shown) in the electronic device 100 may also filter out the sound from the remote end by signal processing. The above noise suppression and algorithm are commonly referred to as a non-stationary noise suppression (NSS) algorithm.
Due to the NSS algorithm, the first audio receiving module 110 and the second audio receiving module 112 utilized by the electronic device 100 adopt audio receiving modules with the same design, or at least audio receiving modules designed with the same gain. However, owing to material selections or errors generated during the manufacturing process, the gains of the first audio receiving module 110 and the second audio receiving module 112 are not necessarily the same. For example, a current acceptable error range of the cell phone manufacturing field is approximately ±3 dB. However, at higher costs, a manufacturer of the electronic device 100 may also obtain a batch of audio receiving modules having a smaller error range, e.g., ±2 dB or even ±1 dB.
Based on industrial design of the electronic device 100, including position factors of the first audio receiving module 110 and the second audio receiving module 112 relative to the audio source 102 as well as error ranges guaranteed by the specific batch of audio receiving modules, the manufacturer calibrates/corrects the electronic devices 100 of every module/batch to generate an audio adjustment value X for the first audio receiving module 110 and the second audio receiving module 112.
Having generated the audio adjustment value X for the electronic device 100 of a particular form, the manufacturer sets the audio adjustment value X into the electronic device 100 of that form. Although being quite convenient, such design has not considered different errors of individual electronic devices 100, meaning different errors in the gains of the first audio receiving module 110 and the second audio receiving module 112 of individual electronic devices 100 may not be properly handled. Consequently, noise suppression effects reflected on individual electronic devices 100 are also inconsistent.
In addition, the audio adjustment value X is obtained by the calibration/correction on the basis of an ideal distance between the electronic device 100 and the audio source 102. In actual applications, as head shapes of users and holding gestures of users may be different, respective distances from the first audio receiving module 110 and the second audio receiving module 112 to mouths of the users are inevitably different from the above ideal distance. Even for the same user, gestures that the user holds the electronic device 100 may also vary.
In summary, with the presence of gain differences between multiple audio receiving modules as well as different application conditions, the result of noise suppression may not be ideal as expected when the audio adjustment value in a constant value X is used as a noise suppression parameter. Therefore, there is a need for a method for calibrating multiple audio receiving modules and for recalibrating an audio adjustment value for individual electronic devices 100 and a user to enhance a noise suppression effect.